Editing Grumman F6F Hellcat (section)

==Design and development==

===XF6F===
[[File:Grumman XF6F-1 Hellcat 1942.jpg|thumb|Unpainted XF6F-1 prior to its first flight (1942)]]
[[File:Ray Wagner Collection Image (16156795450).jpg|thumb|F6F-3 aboard USS ''Yorktown'' has its "[[Grumman Sto-Wing|Sto-Wing]]" folding wings deployed for takeoff (''circa'' 1943-44).]]

Grumman had been working on a successor to the F4F Wildcat since 1938, and the contract for the prototype '''XF6F-1''' was signed on 30 June 1941. The aircraft was originally designed to use the [[Wright R-2600|Wright R-2600 Twin Cyclone]] two-row, 14-cylinder radial engine of {{cvt|1,700|hp|kW}} (the same engine used with Grumman's then-[[Grumman TBF Avenger#Design and development|new torpedo bomber under development]]), driving a three-bladed Curtiss Electric propeller.<ref>Kinzey 1996, p. 16.</ref> Instead of the Wildcat's narrow-track, hand-cranked, main [[landing gear]] retracting into the fuselage inherited from the F3F ( a design from the 1930s [[Grumman FF]]-1 fighter biplane), the Hellcat had wide-set, hydraulically actuated landing-gear struts that rotated through 90° while retracting backwards into the wings, but with full wheel doors fitted to the struts that covered the entire strut and the upper half of the main wheel when retracted, and twisted with the main gear struts through 90° during retraction.<ref name="Taylor p. 503."/> The wing was mounted lower on the fuselage and was able to be hydraulically or manually folded, with each panel outboard of the undercarriage bay folding backwards from pivoting on a specially oriented, Grumman-patented "[[Grumman Sto-Wing|Sto-Wing]]" diagonal axis pivoting system much like the earlier F4F, with a folded stowage position parallel to the fuselage with the leading edges pointing diagonally down.<ref>Kinzey 1987, p. 14.</ref>

Throughout early 1942, [[Leroy Grumman]], along with his chief designers [[Jake Swirbul]] and Bill Schwendler, worked closely with the U.S. Navy's [[Bureau of Aeronautics]] (BuAer) and experienced F4F pilots,<ref>Thruelsen 1976, p. 166.</ref> to develop the new fighter in such a way that it could counter the Zero's strengths and help gain air dominance in the Pacific Theater of Operations.<ref>Ewing 2004, p. 182.</ref> On 22 April 1942, Lieutenant Commander [[Edward O'Hare|Butch O'Hare]] toured the Grumman Aircraft company and spoke with Grumman engineers, analyzing the performance of the F4F Wildcat against the Mitsubishi A6M Zero in aerial combat.<ref name="Ewing Thach Weave p. 86">Ewing 2004, p. 86.</ref>{{refn|On the previous day, while receiving the [[Medal of Honor]] from President [[Franklin D. Roosevelt]], O'Hare was asked by the President what was needed in a new naval fighter; O'Hare's response was "something that would go upstairs faster."<ref>Ewing and Lundstrom 2004, pp. 155–156.</ref>|group=Note}}  Buaer's Lt Cdr A. M. Jackson{{Refn|Jackson emphasized to Grumman, "you can't hit 'em if you can't see 'em"<ref>Tillman 1979, p. 6.</ref>|group=Note}} directed Grumman's designers to mount the cockpit higher in the fuselage.<ref>Francillon 1989, p. 200.</ref> In addition, the forward fuselage sloped down slightly to the engine cowling, giving the Hellcat's pilot good visibility.<ref name="Kin966">Kinzey 1996, p. 6.</ref>

====Change of powerplant====
Based on combat accounts of encounters between the F4F Wildcat and A6M Zero, on 26 April 1942, BuAer directed Grumman to install the more-powerful, 18-cylinder [[Pratt & Whitney R-2800 Double Wasp]] radial engine – which was already in use with Chance Vought's Corsair since 1940 – in the second XF6F-1 prototype.<ref>Ewing and Lundstrom 2004, pp. 155, 156.</ref> Grumman complied by redesigning and strengthening the F6F airframe to incorporate the {{cvt|2,000|hp|kW}} R-2800-10, driving a three-bladed [[Hamilton Standard]] propeller. With this combination, Grumman estimated the XF6F-3s performance would increase by 25% over that of the XF6F-1.<ref name="Sul4"/> The Cyclone-powered XF6F-1 (02981) first flew on 26 June 1942, followed by the first Double Wasp-equipped aircraft, the XF6F-3 (02982), which first flew on 30 July 1942. The first production F6F-3, powered by an R-2800-10, flew on 3 October 1942, with the type reaching operational readiness with [[VF-9]] on {{USS|Essex|CV-9|6}} in February 1943.<ref name= "Kinzey p. 6">Kinzey 1987, p. 6.</ref>{{Refn|Late-production F6F-3s were powered by the same water-injected R-2800 used by the F6F-5.{{citation needed|date=April 2021}}|group=Note}}

===Further development===
[[File:Grumman F6F-3 Hellcat of VF-1 in flight over California (USA), in 1943 (80-G-K-605).jpg|thumb|An early F6F-3 in blue-gray over light gull-gray (1943)]]

The F6F series was designed to take damage and get the pilot safely back to base. A bullet-resistant windshield was used and a total of {{cvt|212|lb}} of cockpit armor was fitted, along with armor around the oil tank and oil cooler. A {{cvt|250|USgal|L}} [[self-sealing fuel tank]] was fitted in the fuselage.<ref name= "Kinzey p. 6"/> Standard armament on the F6F-3 consisted of six .50&nbsp;in (12.7&nbsp;mm) [[M2 Browning machine gun|M2/AN Browning]] air-cooled [[machine gun]]s with 400 rounds per gun. A center-section [[hardpoint]] under the fuselage could carry a single {{cvt|150|USgal|L}} disposable [[drop tank]], while later aircraft had single bomb racks installed under each wing, inboard of the undercarriage bays; with these and the center-section hard point, late-model F6F-3s could carry a total bomb load in excess of {{cvt|2,000|lb}}. Six {{cvt|5|in|mm|0}} [[High Velocity Aircraft Rocket]]s (HVARs) could be carried – three under each wing on "zero-length" launchers.<ref>Sullivan 1979, pp. 24, 30, 33.</ref><ref>Parsch, Andreas. [http://www.designation-systems.net/dusrm/app4/5in-rockets.html "5 inch FFAR/HVAR."] ''designation-systems.net,'' 2010. Retrieved: 28 October 2012.</ref>

Two night-fighter subvariants of the F6F-3 were developed; the 18 F6F-3Es were converted from standard-3s and featured the [[AN/APS-4]] 10&nbsp;GHz frequency radar in a pod mounted on a rack beneath the right wing, with a small radar scope fitted in the middle of the main instrument panel and radar operating controls installed on the port side of the cockpit.<ref>Kinzey 1996, pp. 30–31.</ref> The later F6F-3N, first flown in July 1943, was fitted with the AN/APS-6 radar in the fuselage, with the antenna dish in a bulbous fairing mounted on the leading edge of the outer right wing as a development of the AN/APS-4; about 200 F6F-3Ns were built.<ref>Kinzey 1996, pp. 28–29.</ref> Hellcat night fighters claimed their first victories in November 1943.<ref>Green 1975, p. 91.</ref> In total, 4,402 F6F-3s were built through until April 1944, when production was changed to the F6F-5.<ref name="Kin966"/>

[[File:F6F-5 HVAR NOTS NAN4-2-45.jpg|thumb|An early-production F6F-5 being tested with eight 5-inch HVAR rockets (''circa'' 1944–45)]]

The F6F-5 featured several improvements, including a more powerful R-2800-10W engine employing a water-injection system and housed in a slightly more streamlined engine cowling, spring-loaded control [[Trim tab|tabs]] on the [[aileron]]s, and an improved, clear-view windscreen, with a flat armored-glass front panel replacing the F6F-3's curved plexiglass panel and internal armor glass screen.<ref name="Taylor p. 503.">Taylor 1969, p. 503.</ref><ref name="Kin966"/> In addition, the rear fuselage and tail units were strengthened, and apart from some early production aircraft, most of the F6F-5s built were painted in an overall gloss sea-blue finish.<ref>Kinzey 1996, pp. 6–7.</ref> After the first few F6F-5s were built, the small windows behind the main canopy were deleted.<ref>Kinzey 1996, p. 7.</ref> The F6F-5N night-fighter variant was fitted with an AN/APS-6 radar in a fairing on the outer-starboard wing. A few standard F6F-5s were also fitted with camera equipment for reconnaissance duties as the F6F-5P.<ref>Green 1975, pp. 93–94.</ref> While all F6F-5s were capable of carrying an armament mix of one 20-mm (.79-in) [[Hispano-Suiza HS.404#US production|M2 cannon]] in each of the inboard gun bays (220 rounds per gun), along with two pairs of .50-in (12.7-mm) machine guns (each with 400 rounds per gun), this configuration was only used on later F6F-5N night fighters.<ref name= "Kinzey p. 27">Kinzey 1987, p. 27.</ref> The F6F-5 was the most common F6F variant, with 7,870 being built.<ref name="Kin966"/>{{Refn|US produced 20 mm cannon were troubled by reliability issues delaying their introduction {{citation needed|date=April 2021}} |group=Note}}

Other prototypes in the F6F series included the XF6F-4 (02981, a conversion of the XF6F-1 powered by an R-2800-27 and armed with four 20-mm M2 cannon), which first flew on 3 October 1942 as the prototype for the projected F6F-4. This version never entered production and 02981 was converted to an F6F-3 production aircraft.<ref>Kinzey 1996, p. 32.</ref> Another experimental prototype was the XF6F-2 (66244), an F6F-3 converted to use a Wright R-2600-15, fitted with a Birman-manufactured mixed-flow [[turbocharger]], which was later replaced by a Pratt & Whitney R-2800-21, also fitted with a Birman turbocharger.<ref>White 2001, pp. 260, 508.</ref> The turbochargers proved to be unreliable on both engines, while performance improvements were marginal. As with the XF6F-4, 66244 was soon converted back to a standard F6F-3.<ref>Kinzey 1996, pp. 17–18.</ref> Two '''XF6F-6s''' (70188 and 70913) were converted from F6F-5s and used the 18-cylinder {{cvt|2,100|hp|kW|0}} Pratt and Whitney R-2800-18W two-stage supercharged radial engine with water injection and driving a Hamilton-Standard four-bladed propeller.<ref>Kinzey 1996, pp. 50–51.</ref> The XF6F-6s were the fastest version of the Hellcat series with a top speed of {{cvt|417|mph|km/h|0|abbr=on}}, but the war ended before this variant could be mass-produced.<ref name="Taylor p. 503."/><ref>Sullivan 1979, p. 46.</ref> The last Hellcat rolled out in November 1945, the total production being 12,275, of which 11,000 had been built in just two years.<ref>Winchester 2004, p. 110.</ref> This high production rate was credited to the sound original design, which required little modification once production was under way.